The subject matter of the invention relates to branched, high-molecular, soluble, thermoplastic, aromatic polyaryl-ether sulphones, obtained by the reaction in polar organic solvents of aromatic dialkali metal bishydroxylates (dialkali metal bisphenolates) with bis-(4-halogenaryl) compounds, whose aryl nuclei are linked by sulphonyl groups, and with three or more than three functional aromatic alkali metal hydroxylates and/or such halogen-aryl compounds, which have three or more aryl-linked halogen substituents capable of substitution under the reaction conditions prevailing in the manufacture of polyaryl ether sulphones.
Films and moldings from these branched polyaryl-ether sulphones, in contrast to those from linear polyaryl-ether sulphones, surprisingly show improved resistance to unsaturated polyester resins, reduced inflammability and little susceptibility to stress cracking.
Linear polyaryl-ether sulphones, for example, which are obtained in accordance with Dutch patent application No. 6 408 130, fail to be of use as electro-insulating foils because of their low resistance to solvents and, in particular, to unsaturated polyester resins when the insulated parts are cast with them (H. Glaser, Kunststoffe Issue No. 4, (1971), p. 234, and J. Buhlmann industrie-elektrik + elektronik no. 20 (1972) p. 514).
The branched aromatic polyaryl-ether sulphones according to the invention do not exhibit these disadvantages.